How to convert Cycles materials into LuxCore materials and have textures still applied?
When using a new render engine, many things will change in your scene. There will be an entirely new lighting system, your textures will no longer look correct (although all your UV's will still be good).

The render settings will be completely different, another engine will have different rendering features than Cycles. Render Passes will be handled different, the lighting values will drastically change and may not even work at all. Some render engines (in my case Renderman) requires you to use a separate program called "IT" to render to, you can no longer use your Blender view port to see your renders. 

To sum it up:

You will have to redo all your lights, textures, and will have to learn the new settings to best optimize your scene. There is no button to just transfer everything to a new render engine. 

Also keep in mind, you may not be able to use any GPU's to render out your scene, I am not sure if this is true for LuxCore but  this is the reason I quit using Renderman.